Prevalence of Tobacco Use among Junior High and Senior High School Students in Taiwan

(1)

R

E S E A R C H

A

R T I C L E

Prevalence of Tobacco Use Among

Junior High and Senior High School

Students in Taiwan

PING-LINGCHEN, PhDa

WEIGANGHUANG, MAb YI-LICHUANG, MSc CHARLESW. WARREN, PhDd NATHANR. JONES, PhDe SAMIRAASMA, DDSf

ABSTRACT

BACKGROUND: Tobacco use is a major preventable cause of death in the world. This article describes and compares tobacco use prevalence for students attending junior high schools and senior high schools in Taiwan.

METHODS: This report uses data from the Global Youth Tobacco Survey (GYTS) com-pleted among 4689 junior high school students and 4426 senior high school students in Taiwan in 2004-2005. The GYTS uses a 2-stage sampling design to produce nationally representative data for junior and senior high students in general and vocational schools. RESULTS: Higher smoking prevalence was observed among senior high (10.1% gen-eral schools and 15.9% vocational schools) than junior high (5.5%) school students. Smoking prevalence of girls in junior high (3.2%) and senior high schools (4.6% gen-eral and 11.1% vocational) was almost as high or higher than adult females’ (4.3%) smoking rates. The pattern of smoking intensity across school years and type of school shows that the percentage of smokers who were experimenters (47.1%) was higher in junior high school and the percentage of smokers who were

regular/established smokers (over 50%) was higher in senior high school.

CONCLUSIONS: Smoking prevalence described in this report shows that there are chal-lenges facing the tobacco prevention and control program in Taiwan. The findings suggest that schools should increase their smoking initiation prevention efforts and make available cessation programs and counseling to help students quit smoking. If effective youth tobacco control programs are not developed and implemented in Taiwan, future morbidity and mortality attributed to tobacco will surely increase, especially among women.

Keywords: tobacco; schools; surveillance; Taiwan.

Citation: Chen PL, Huang W, Chuang YL, Warren CW, Jones NR, Asma S. Prevalence of tobacco use among junior high and senior high school students in Taiwan. J Sch Health. 2008; 78: 649-654.

a

Associate Professor, (plchen@tmu.edu.tw), Taipei Medical University, No. 250, Wu-Hsing St, Taipei 110, Taiwan.

b

Bureau of Health Promotion, Taiwan Department of Health, Taiwan, 5thFl, No. 503, Sec 2, Li Ming Rd, Taichung 408, Taiwan.

c

Director of Population and Health Research Center, (yilic@bhp.doh.gov.tw), Bureau of Health Promotion, Department of Health, Taiwan, 5th Fl, No. 503, Sec 2, Li Ming Rd, Taichung 408, Taiwan.

d

Statistician/Demographer, (wcw1@cdc.gov), 4770 Buford Hwy, NE, MS-K50, Atlanta, GA 30341-3717.

e

Director, (naj5@cdc.gov), Survey Research Shared Service, Paul P. Carbone Comprehensive Cancer Center, University of Wisconsin, Madison, Wisconsin.

f_{Associate Director, (sea5@cdc.gov), Global Tobacco Control Program, Office on Smoking and Health, Centers for Disease Control and Prevention, 4770 Buford Hwy, NE, MS-K50,}

Atlanta, GA 30341-3717.

(2)

T

obacco use is a major preventable cause of death in the world. The World Health Organization (WHO) attributes over 4 million deaths per year to tobacco, a figure that is expected to increase to 10 mil-lion deaths a year by 2020.1Almost half (46.8%) of adult men and 4% of adult women in Taiwan are smokers, resulting in over 18,000 deaths from tobacco-related dis-eases each year.2,3 Lung cancer is the second leading cause of cancer death in Taiwan.4Studies have found that tobacco use most often begins during adolescence.5 Results from the 2001 Taiwan National Health Inter-view Survey suggest that tobacco control efforts in Taiwan face several challenges: low quit rates among males, high exposure to secondhand smoke, a sharp increase in smoking prevalence after students leave high school, and the potential for rapid increase in female smoking if prevalence of smoking among girls persists into adulthood.3The Bureau of Health Promo-tion (BHP) in Taiwan was established in 2003 and has made tobacco use prevention among adolescents a pri-mary health issue.

Surveillance of tobacco use is necessary in order to plan, evaluate, and revise tobacco control program efforts. Previous research on tobacco in Taiwan used a number of survey instruments, sampling frames, and data collection protocols. Because of these differ-ences, data from these surveys are not comparable to each other or to data from other countries. In order to address the need for comparable data, Taiwan imple-mented the Global Youth Tobacco Survey (GYTS) in 2004-2005. The GYTS, part of the Global Tobacco Sur-veillance System initiated by WHO, US Centers for Disease Control and Prevention, and the Canadian Public Health Association, was developed to monitor youth tobacco use, attitudes, and exposure to second-hand smoke among adolescents aged 13-15 years using standardized methods and has been completed by over 2 million students in 150 countries.6In 2004, Taiwan conducted the GYTS in junior high schools to gather information for 13- to 15-year-old students. In 2005, Taiwan expanded the GYTS to include general and voca-tional senior high schools to gather information for 16-to 18-year-old students.

The purposes of this article are to describe and com-pare tobacco use prevalence for students attending junior and senior high schools in Taiwan. The analy-ses will focus on 3 groups of students: junior high, general senior high, and vocational senior high. METHODS

Procedure

GYTS uses standardized methods for constructing sampling frames, selecting schools and classes, prepar-ing questionnaires, carryprepar-ing out field procedures, and processing data. The GYTS questionnaire is self-adminis-tered in classrooms, and school, class, and student

ano-nymity is maintained throughout the GYTS process. The GYTS questionnaire was translated into Chinese and checked for accuracy and comprehension in Taiwan.

Subject

The GYTS was implemented in Taiwan among junior and senior secondary students in 2004 and 2005, respectively. These surveys targeted students in all 3 grades of junior secondary schools and all 3 grades of senior secondary general and vocational schools. For the most part, general senior high school graduates will go to a university for further education, and voca-tional high school graduates will enter the job market with the professional training they received at school. Junior and senior high samples were drawn from comprehensive lists of all schools that included the target grades. Schools were selected for participation proportional to total enrollment in the targeted grades, and classes were selected for participation through systematic random selection within schools.

Instrument

The GYTS core questionnaire includes items on prevalence of cigarette and other tobacco use, percep-tions and attitudes about tobacco, access to and avail-ability of tobacco products, exposure to secondhand smoke, school curricula, media and advertising, and smoking cessation. Estimates in this article are pre-sented for measures of tobacco use prevalence and cigarette smoking intensity among current cigarette smokers. The measures of smoking prevalence include lifetime cigarette smoking status (ever smokers are defined as the percentage of students who responded ‘‘Yes’’ to the question, ‘‘Have you ever smoked a ciga-rette, even one or two puffs?’’), current cigarette smoking status (current smokers are defined as the percentage of students who responded 1 or more days to the question, ‘‘During the past 30 days (1 month), on how many days did you smoke cigarettes?’’), and tobacco use in forms other than cigarettes (other tobacco users are defined as the percentage of stu-dents who answered ‘‘Yes’’ to the question, ‘‘During the past 30 days (one month), have you ever used any form of tobacco products other than cigarettes (e.g. chewing tobacco, snuff, dip, cigars, cigarillos, lit-tle cigars, pipe)?’’ Among current smokers, estimates of smoking intensity are presented for experimenters (defined as current smokers who smoked 5 or fewer days in the past month) and regular/established smokers (defined as current smokers who smoked 20 or more days in the past month).

Data Analysis

Taiwan GYTS data were weighted to adjust for sam-ple selection (school and class levels), nonresponse

(3)

(school, class, and students levels), and poststrati-fication of the sample population relative to the grade and sex distribution in the total population. SUDAAN7 was used to calculate weighted prevalence estimates and standard errors (SEs) of the estimates (95% confidence intervals were calculated from the SEs). Dif-ferences in proportions were considered statistically significant at the p , .05 level.

RESULTS Response Rates

Both the junior high and the senior high samples were stratified by urbanization (ie, large city, small city, small town, rural). The junior high sample included 52 schools and the senior high 61 schools. The school response rate was 100% for both, and the student response rate was 97.0% for the junior high and 93.4% for the senior high. In total, 4689 students participated in the junior high survey, and 4426 stu-dents participated in the senior high survey. For the senior high, 2074 students were in general schools and 1844 in vocational schools. The remaining 508 students attended night schools and were excluded from this study.

Smoking Status

Overall, 25.5% of junior high students, 34.0% of general senior high students, and 46.7% of vocational senior high students had ever smoked a cigarette (Table 1). Vocational senior high students were signi-ficantly more likely than junior high students to have ever smoked cigarettes. Boys and girls in vocational high schools were significantly more likely than boys and girls in junior high schools to have ever smoked cigarettes. Among senior high students, girls in voca-tional schools were significantly more likely than girls

in general schools to have ever smoked a cigarette. Boys were significantly more likely than girls to have ever smoked cigarettes among junior high and general senior high students.

Overall, 5.5% of junior high students, 10.1% of general senior high students, and 15.9% of vocational senior high students currently smoked cigarettes (Table 1). Vocational senior high students were signi-ficantly more likely than junior high students to cur-rently smoke cigarettes, overall and among both boys and girls. Boys were significantly more likely than girls to currently smoke cigarettes in junior high.

Vocational senior high year 1 students were 2.6 times more likely to currently smoke than year 3 stu-dents in junior high, whereas general senior high year 1 students were only 1.1 times more likely than year 3 junior high students to currently smoke (Figure 1). Vocational senior high school students were more likely to currently smoke than general senior high school students at each year in school but the differ-ential varied (2.3 times higher at year 1, 1.2 times higher at year 2, and 1.5 times higher at year 3). For general senior high school students, the pattern of smoking prevalence between the years shows that year 2 was 1.7 times higher than year 1, but the rates are similar in years 2 and 3. For vocational senior high school students, the pattern was inconsistent with year 1 lower than year 2 and the rate for year 3 similar to year 1.

Smoking Intensity

Smoking intensity varied significantly among

junior high and senior high students (Table 2). Almost half (47.1%) of junior high students who cur-rently smoke were experimenters compared to about 3 in 10 senior high students (28.9% for both general and vocational senior high students). In comparison,

Table 1. Prevalence of Tobacco Use by Type of School and Sex—Taiwan, GYTS, 2004 Junior High and 2005 Senior High* Type of School and Sex Ever Smoked Cigarettes,†% (95% CI) Currently Smoke Cigarettes,‡% (95% CI) Current Other Tobacco Use,§% (95% CI) Junior high Total 25.5 (23.4-27.8) [4573] 5.5 (4.7-6.3) [4559] 4.0 (3.5-4.7) [4638] Boy 30.8 (28.7-33.0) [2250] 7.4 (6.2-8.7) [2227] 4.8 (4.0-5.7) [2283] Girl 19.8 (17.6-22.2) [2255] 3.2 (2.4-4.3) [2263] 3.3 (2.6-4.0) [2284] Senior high—general Total 34.0 (25.8-43.2) [2055] 10.1 (5.1-19.0) [2040] 5.5 (3.6-8.2) [2074] Boy 43.3 (30.3-57.3) [970] 15.6 (7.4-30.0) [955] 7.5 (4.4-12.4) [977] Girl 24.2 (19.1-30.2) [1055] 4.6 (2.4-8.9) [1055] 3.6 (2.5-5.2) [1068] Senior high—vocational Total 46.7 (40.3-53.2) [1813] 15.9 (11.3-21.8) [1800] 5.9 (4.2-8.0) [1843] Boy 50.4 (42.6-58.1) [882] 20.3 (12.7-30.7) [871] 7.2 (4.7-10.8) [894] Girl 42.2 (34.3-50.5) [891] 11.1 (7.0-17.1) [891] 4.5 (2.4-8.3) [910]

*The values within square brackets indicate unweighted number of cases. Differences across cells occur due to nonresponse and consistency/logic edits.

†

Ever smoked cigarettes, even 1 or 2 puffs.

‡

Smoked cigarettes on 1 or more days during the past 30 days (month).

(4)

over half of senior high students (53.9% general and 51.4% vocational) were regular/established smokers compared to 25.9% among junior high students. In all 3 types of schools, girls were more likely than boys to be experimenters and less likely to be regular/estab-lished smokers. For junior high year 1, 66.8% of the smokers were experimenters, but by year 3 of senior high school, the percent experimenters was 21.7% for general and 23.4% for vocational smokers (Table 3). In contrast, for junior high year 1, 20.1% of the smokers were regular/established smokers, but by year 3 of senior high school, the percent regular/established was 60.7% for general and 62.1% for vocational smokers. Tobacco Use Other Than Cigarettes

Overall, 4.0% of junior high students, 5.5% of gen-eral senior high students, and 5.9% of vocational senior high students currently used tobacco products other than cigarettes (Table 1). There were no significant differences in other tobacco use by gender or type of school.

DISCUSSION

The Taiwan GYTS data collected in 2004 and 2005 provided a nationally representative and internation-ally comparable source of information on tobacco-related behavior and attitudes for adolescents. Data from 13- to 15-year-olds in the Taiwan junior high GYTS can be compared to GYTS data for 13- to 15-year-olds from other countries in the Western Pacific. Current cigarette smoking among 13- to 15-year-old students in Taiwan (5.5%) was similar to the Western Pacific region average (6.5%).5Comparing individual

countries in the Western Pacific region, the rate for boys in Taiwan (7.4%) was similar to that of boys in 3 sites in China: Guangdong (6.7%), Shandong (4.6%), and Macao (8.1%). Prevalence of smoking among boys was higher in Fiji (13.1%), Northern Mariana Islands (40.7%), Palau (20.0%), Philippines (26.2%), and Sin-gapore (10.5%).8The rate for girls in Taiwan (3.2%) was similar to that for 5 sites in China: Chongqing (1.9%), Guangdong (2.2%), Shandong (0.2%), Tianjin (1.5%), and Macao (5.6%) but lower than in Fiji (7.1%), Northern Mariana Islands (37.5%), Palau (23.3%), Philippines (12.4%), and Singapore (7.5%).8 Findings from the Taiwan junior high GYTS raised concerns at the BHP regarding the tobacco control effort in Taiwan. First, the prevalence of smoking for girls in junior high (3.2%) is almost as high as adult

females in Taiwan (4.3%);2 the smoking prevalence

for girls in both the general high school (4.6%) and the vocational senior high school (11.1%) was higher. Smoking prevalence for girls in vocational high schools was 2.6 times higher than for adult females. Second, the prevalence of smoking for boys in junior high (7.4%) was considerably lower than for adult males in Taiwan (46.8%). The smoking prevalence for boys in general high schools (15.6%) was more than double that of junior high boys; however, the adult male rate was still 3 times higher. For boys in vocational high schools (20.3%), prevalence was almost 3 times higher than for boys in junior high, and the adult male rate was only 2.3 times higher. Findings from the GYTS are consistent with the results reported by Wen et al3 using the 2001 Taiwan National Health Interview Sur-vey. These results suggest that smoking by females,

Figure 1. Percentage of Students Who Currently Smoked Cigarettes by Grade and Type of School, Taiwan, GYTS, 2004-2005

6.2 6.6 3.7 11.8 _11.5 7.1 17.4 16.3 13.7 0 5 10 15 20 25 30 Jr1 Jr2 Jr3 Sr1 Sr2 Sr3 Grade Percent Jr Sr Gen Sr Voc

(5)

especially young girls, should be a priority in Taiwan. This is consistent with previous studies on the preva-lence of smoking among young girls in many Western Pacific countries.8 For decades, the tobacco industry has targeted females and continues to expand this

market.9,10 The tobacco industry targets women

through advertisements showing smoking associated with independence, stylishness, weight control, sophistication, and power.11

The Taiwan GYTS also found differences in smok-ing intensity between junior high and senior high smokers. The pattern of smoking intensity across years and type of school shows that the percentage of smokers who are experimenters is higher in junior high school and the percentage of smokers who are regular/established smokers is higher in senior high school. These findings are consistent with much of the work that has conceptualized adolescent smoking as a progression across stages based on smoking fre-quency and intensity.12-15 These stages frequently include preparation, initial trying, experimentation, and regular/established use.12,13 Several studies have found that age or grade in school has a strong positive association with regular/established smoking among adolescents.14,15

How can Taiwan use the findings from the junior high and senior high GYTS to assist in developing their tobacco control program? In general, the main goal of a comprehensive tobacco control program is to improve the health of the population by encouraging smokers to quit, eliminating exposure to secondhand smoke, and encouraging people not to initiate tobacco use. Previous studies have shown that demand reduc-tion measures, primarily those that increase the price of tobacco, are effective in significantly reducing initi-ation of tobacco use and consumption among young people.16In addition to demand reduction measures, comprehensive tobacco control programs often include nonprice interventions such as restrictions on smoking in public places and workplaces, a complete ban on advertising and promotion by tobacco companies, dis-semination of information on the health consequences of smoking through various media such as prominent warning labels on cigarette packets and countermar-keting campaigns, and development and

implemen-tation of school-based educational programs in

combination with community-based activities.16,17 Taiwan should consider a range of components when developing and implementing tobacco prevention and control strategies. Tobacco control efforts for adolescents

Table 2. Smoking Intensity Among Current Cigarette Smokers†by Type of School and Sex—Taiwan, GYTS, 2004 Junior High and 2005 Senior High*

Junior High Total, % (95% CI) Boy, % (95% CI) Girl, % (95% CI)

Experimenters‡ 47.1 (41.8-52.5) [242] 43.3 (37.4-49.3) [162] 56.4 (42.5-69.4) [72] Regular/establishedx 25.9 (20.7-31.9) [242] 28.8 (21.8-37.0) [162] 18.7 (11.6-28.6) [72] Senior high—general Experimenters‡ 28.9 (15.8-47.0) [207] 24.2 (11.0-45.4) [152] 45.1 (22.6-69.7) [51] Regular/establishedx 53.9 (35.0-71.7) [207] 59.0 (36.4-78.3) [152] 37.2 (19.9-58.5) [51] Senior high—vocational Experimenters‡ 28.9 (19.9-40.0) [277] 24.9 (15.5-37.4) [168] 38.1 (23.6-55.1) [98] Regular/establishedx 51.4 (39.5-63.1) [277] 59.5 (44.6-72.8) [168] 35.7 (24.6-48.6) [98]

†

‡

Experimenters are current smokers who smoked 5 or fewer days in the past 30 days (month).

x_{Regular/established smokers are current smokers who smoked 20 or more days in the past 30 days (month).}

Table 3. Smoking Intensity Among Current Cigarette Smokers†by Type of School and Year in School—Taiwan, GYTS, 2004 Junior High and 2005 Senior High*

Junior High Total, % (95% CI) Year 1, % (95% CI) Year 2, % (95% CI) Year 3, % (95% CI)

Experimenters‡ _{47.1 (41.8-52.5) [242]} _{66.8 (56.0-76.1) [57]} _{44.5 (32.3-57.4) [105]} _{38.6 (27.6-51.0) [77]} Regular/establishedx 25.9 (20.7-31.9) [242] 20.1 (12.6-30.4) [57] 23.5 (17.1-31.5) [105] 30.6 (20.3-43.2) [77] Senior high—general Experimenters‡ _{28.9 (15.8-47.0) [207]} _{37.1 (15.6-65.3) [58]} _{30.3 (12.3-57.3) [78]} _{21.7 (9.1-43.4) [70]} Regular/establishedx 53.9 (35.0-71.7) [207] 43.6 (22.8-66.8) [58] 55.1 (23.5-83.1) [78] 60.7 (40.2-78.1) [70] Senior high—vocational Experimenters‡ 28.9 (19.9-40.0) [277] 33.5 (17.0-55.4) [104] 29.5 (15.4-48.9) [86] 23.4 (9.9-45.9) [80] Regular/establishedx 51.4 (39.5-63.1) [277] 45.1 (23.7-68.4) [104] 47.5 (25.9-70.1) [86] 62.1 (46.1-75.9) [80]

†

‡

Experimenters are current smokers who smoked 5 or fewer days in the past 30 days (month).

x

(6)

can benefit from a multicomponent approach that in-volves the school environment. The school component could include elements that provide information about the dangers of smoking; improve understanding of media, peer, and family influences; and teach refusal skills. Also, implementing and enforcing tobacco-free school policies can protect students from secondhand smoke exposure and reduce the social acceptability of tobacco use. These school-based initiatives reach their maximum effectiveness working with an effective broader tobacco control program.18

Limitations

The findings in this report are subject to at least 3 limitations. First, because GYTS is limited to students, the survey might not be representative of all youths aged 13-18 years. However, in Taiwan, junior high school attendance is compulsory, and the gross enroll-ment rate for senior high schools was over 95% in 2005.19 Second, these data apply only to youths who were in school on the day of the survey and who com-pleted the survey. However, school response rates were 100%, and student response rates were very high (more than 90%), suggesting that bias attributable to absence or nonresponse was limited. Finally, data were based on the self-report of students, who might underreport or over-report their behaviors or attitudes. The extent of this bias cannot be determined from these data; however, reliabil-ity studies in the United States have indicated good test-retest results for similar tobacco-related questions.20

CONCLUSIONS

Smoking prevalence among students described in this report shows that there are opportunities to improve tobacco control and prevention in Taiwan. Taiwan GYTS data indicated that smoking prevalence was significantly higher among senior high than junior high school students. Furthermore, higher smoking prevalence among girl students is an emerg-ing challenge for tobacco control in Taiwan as it is for many countries in Asia. The majority of smokers in junior high school were experimenters, but the per-centage of regular/established smokers was signifi-cantly higher among senior high school students. These findings suggest that, in conjunction with a broader tobacco control program and in addition to smoking initiation prevention efforts in junior and senior high schools, schools should develop and make available cessation programs and counseling to help students quit smoking in senior high. If effective youth tobacco control programs are not developed and implemented in Taiwan, future morbidity and mortality attributed to tobacco will surely increase, especially among women. Ongoing surveillance is necessary to track trends and patterns of youth

smok-ing among different school programs as a means of evaluating youth tobacco control program efforts.

REFERENCES

1. Peto R, Lopez AD, Boreham J, Thun M, Heath C Jr. Mortality From Smoking in Developed Countries 1950-2000: Indirect Estimation From National Vital Statistics. Oxford, England: Oxford University Press; 1994.

2. Cheng TY, Wen CP, Tsai MC, Tsai SP. The current status of smok-ing behavior in Taiwan: data analysis from National Health Inter-view Survey in 2001. Taiwan J Public Health. 2002;22(6):453-464. 3. Wen CP, Levy DT, Yuan Cheng T, Hsu CC, Tsai SP. Smoking behavior in Taiwan, 2001. Tob Control. 2005;14(suppl 1):i51-i55. 4. Taiwan Cancer Registration System Annual Report, 2004. 2005. Available at: http://crs.cph.ntu.edu.tw/crs_c/index.htm. Accessed May 2007.

5. US Department of Health and Human Services. Preventing Tobacco Use Among Young People: A Report of the Surgeon General. Atlanta, Ga: US Department of Health and Human Services, Public Health Service, Centers for Disease Control and Health Promotion, Office on Smoking and Health; 1994.

6. Warren CW, Jones NR, Eriksen MP, Asma S. Patterns of global tobacco use in young people and implications for future chronic disease burden in adults. Lancet. 2006;367(9512):749-753. 7. Shah BV, Barnwell BG, Bieler GS. Software for the Statistical

Anal-ysis of Correlated Data (SUDAAN): User’s Manual, Release 7.5, 1997 [software documentation]. Research Triangle Park, NC: Research Triangle Institute; 1997.

8. The Global Youth Tobacco Survey Collaborative Group. Differ-ences in worldwide tobacco use by gender: findings from the Global Youth Tobacco Survey. J Sch Health. 2003;73(6):207-215. 9. Pierce J, Choi WS, Gilpin EA, et al. Tobacco industry promotion of cigarettes and adolescent smoking. JAMA. 1998;279(7):505-511. 10. Hochberg A. Critics fume over marketing of ‘‘Camel No. 9.’’ NPR, March 16, 2007. Available at: www.npr.org/templates/story/ story.php?storyld+8909745. Accessed May 2007.

11. Campaign for Tobacco-Free Kids. Tobacco industry targeting of women and girls. CTFK Factsheet, May 7, 2007.

12. Leventhal H, Cleary PD. The smoking problem: a review of the research and theory in behavioral risk modification. Psychol Bull. 1980;88:370-405.

13. Flay BR. Youth tobacco use: risks, patterns, and control. In: Orleans CT, Slade J, eds. Nicotine Addiction: Principles and Manage-ment. New York, NY: Oxford University Press; 1993:365-384. 14. Mowery PD, Farrelly MC, Haviland L, Gable JM, Wells HE.

Pro-gression to established smoking among US youths. Am J Public Health. 2004;94(2):331-337.

15. Lloyd-Richardson EE, Papandonatos G, Kazura A, Stanton C, Niaaura R. Differentiating stages of smoking intensity among adolescents: stage-specific psychological and social influences. J Consult Clin Psychol. 2002;70(4):998-1009.

16. Jha P, Chaloupka FJ. Curbing the Epidemic: Governments and the Economics of Tobacco Control. Washington, DC: World Bank; 1999. 17. Jha P, Chaloupka FJ. Tobacco Control in Developing Countries.

Oxford, England: Oxford University Press; 2000.

18. The Task Force on Community Preventive Services. Recommen-dations regarding interventions to reduce tobacco use and expo-sure to environmental tobacco smoke. Am J Prev Med. 2001; 20(suppl):10-15.

19. Taiwan Ministry of Education. Educational Statistical Indicators. Taipei, Taiwan Ministry of Education, Republic of China (Taiwan); 2006. Available at: http://english.moe.gov.tw. Accessed May 2007. 20. Brener ND, Kann L, McManus T, Kinchen SA, Sundberg EC, Ross JG. Reliability of the 1999 Youth Risk Behavior Survey question-naire. J Adolesc Health. 2002;31:336-342.